水–岩作用下断续节理砂岩力学特性劣化机理

在库水位周期性升降作用下,库水消落带节理岩体的损伤劣化很可能导致库岸边坡向不稳定的方向发展。基于此,开展了断续节理砂岩的水–岩作用试验,结合力学试验和微细观结构检测综合分析其劣化规律及机理。结果显示:(1)在长期水–岩作用过程中,断续节理岩样的抗压强度、变形模量劣化趋势明显,而且存在明显非均匀性,其中前3个水-岩作用周期的阶段劣化度明显较大,5个水–岩作用周期之后的阶段劣化度明显减小并趋于稳定。(2)水–岩作用下,不同节理倾角岩样的力学参数劣化幅度不一样,阶段劣化度总体呈U型分布,节理倾角在0°和90°附近时,节理岩样从明显的张性破坏逐渐向剪性破坏转变,破坏模式变化特征比较明显,对应力学参数劣化幅度较大;节理倾角为60°左右时,节理岩样总体保持顺节理面的剪切破坏,破坏模式变化特征不明显,对应力学参数劣化幅度比较小,这些变化也使得节理岩样各向异性力学特征逐渐减弱。(3)在水库长期运行过程中,消落带节理岩体的产状直接影响水–岩作用的劣化趋势和变形破坏特征,因此,在库岸边坡长期变形稳定分析中,不仅要关注消落带岩体力学性质的劣化,也要关注节理岩体的产状差异及其在水–岩作用下变形破坏模式的转化。

Degradation mechanism of intermittent jointed sandstone under water-rock interaction

Under the action of periodic rising and falling of reservoir water level, the damage and deterioration of the jointed rock mass in the hydro-fluctuation belt of a reservoir bank slope is likely to cause the reservoir bank slope to develop in an unstable direction. Based on this, the water-rock interaction tests on the intermittent joint sandstone are carried out. The degradation law and mechanism are comprehensively analyzed by combining the mechanical tests and the micro-structure detection. The results show that:(1) In the long-term process of water-rock interaction, the compressive strength and deformation modulus of intermittent jointed rock samples exhibit obvious tendency of deterioration, and there are obvious non-uniformity. Among them, the stage deterioration degree caused by the first three water-rock interaction periods is obviously larger, and the stage deterioration degree obviously decreases and tends to be stable after the five water-rock interaction periods.(2) Under the water-rock interaction, the mechanical parameters of different joint dip angles have different degradation degrees, and the overall distribution of stage deterioration degrees is U-shaped. When the joint dip angle is around 0° or 90°, the jointed rock sample changes from obvious tensile failure to shear one. The change characteristics of failure mode are obvious, and the corresponding mechanical parameters deteriorate greatly. When the joint dip angle is about 60°, the jointed rock sample maintains the shear failure of the joint plane as a whole, and the failure mode change characteristics are not obvious, and the corresponding mechanical parameters have a relatively small extent. These changes also make the anisotropic mechanical properties of jointed rock samples gradually weakened.(3) During the long-term operation of the reservoir bank slope, the occurrence of jointed rock mass in the hydro-fluctuation belt directly affects the deterioration trend and deformation and failure characteristics of the water-rock interaction. Therefore, in the long-term deformation stability analysis of the bank slope, attention should be paid to the deterioration of mechanical properties of rock mass in the hydro-fluctuation belt and the occurrence difference of jointed rock mass and transformation of its deformation and failure mode under water-rock interaction.